Figure 1.

The analysis of the CaM structures in apo and Ca²⁺ bound conformations as well as in complex with the target PKII molecule. The apo (1DMO [18]) (A) and Ca²⁺ bound (1CLL [19]) (B) structures of the CaM protein illustrate Ca²⁺ induced conformational transitions. (C) The backbone representation of the calcium bound form (1CLL [19]) highlights the pairwise proximity of the (red and blue, violet and brown) Ca²⁺ binding EF hand domains and at the same time raises doubts about overall cooperativity between binding sites. (D) Structure of the Ca²⁺ loop on the N-terminal of the CaM protein (1CLL [19]). The dotted line shows the interaction between oxygen atoms on the sidechains of Asp20, Asp22, Asp24, Thr26, Glu31 residues and Ca²⁺ or Mg²⁺ ions. (E) The ribbon diagram of the Ca²⁺-CaM in complex with the target peptide of the protein kinase kinase (1CKK [22]).